Buggy code:
public static final String TOKEN_END = "@" ; private String name ; private Hashtable properties = new Hashtable ( ) ; private Hashtable userProperties = new Hashtable ( ) ; private Hashtable references = new Hashtable ( ) ; private String defaultTarget ; private Hashtable dataClassDefinitions = new Hashtable ( ) ; private Hashtable taskClassDefinitions = new Hashtable ( ) ; private Hashtable targets = new Hashtable ( ) ; private Hashtable filters = new Hashtable ( ) ; private File baseDir ; private Vector listeners = new Vector ( ) ; private static Method setLastModified = null ; private static Object lockReflection = new Object ( ) ; public Project ( ) { } public void init ( ) throws BuildException { } public void addBuildListener ( BuildListener listener ) { } public void removeBuildListener ( BuildListener listener ) { } public Vector getBuildListeners ( ) { } public void log ( String msg ) { } public void log ( String msg , int msgLevel ) { } public void log ( Task task , String msg , int msgLevel ) { } public void log ( Target target , String msg , int msgLevel ) { } public void setProperty ( String name , String value ) { } public void setUserProperty ( String name , String value ) { } public String getProperty ( String name ) { } public String getUserProperty ( String name ) { } public Hashtable getProperties ( ) { } public Hashtable getUserProperties ( ) { } public void setDefaultTarget ( String defaultTarget ) { } public String getDefaultTarget ( ) { } public void setDefault ( String defaultTarget ) { } public void setName ( String name ) { } public String getName ( ) { } public void addFilter ( String token , String value ) { } public Hashtable getFilters ( ) { } public void setBasedir ( String baseD ) throws BuildException { } public void setBaseDir ( File baseDir ) { } public File getBaseDir ( ) { } public static String getJavaVersion ( ) { } public void setJavaVersionProperty ( ) { } public void addTaskDefinition ( String taskName , Class taskClass ) { } public Hashtable getTaskDefinitions ( ) { } public void addDataTypeDefinition ( String typeName , Class typeClass ) { } public Hashtable getDataTypeDefinitions ( ) { } public void addTarget ( Target target ) { } public void addTarget ( String targetName , Target target ) throws BuildException { } public void addOrReplaceTarget ( Target target ) { } public void addOrReplaceTarget ( String targetName , Target target ) { } public Hashtable getTargets ( ) { } public Task createTask ( String taskType ) throws BuildException { } public Object createDataType ( String typeName ) throws BuildException { } public void executeTargets ( Vector targetNames ) throws BuildException { } public void executeTarget ( String targetName ) throws BuildException { } public File resolveFile ( String fileName , File rootDir ) { } public File resolveFile ( String fileName ) { } public static String translatePath ( String to_process ) { } public void copyFile ( String sourceFile , String destFile ) throws IOException { } public void copyFile ( String sourceFile , String destFile , boolean filtering ) throws IOException { } public void copyFile ( String sourceFile , String destFile , boolean filtering , boolean overwrite ) throws IOException { } public void copyFile ( String sourceFile , String destFile , boolean filtering , boolean overwrite , boolean preserveLastModified ) throws IOException { } public void copyFile ( File sourceFile , File destFile ) throws IOException { } public void copyFile ( File sourceFile , File destFile , boolean filtering ) throws IOException { } public void copyFile ( File sourceFile , File destFile , boolean filtering , boolean overwrite ) throws IOException { } public void copyFile ( File sourceFile , File destFile , boolean filtering , boolean overwrite , boolean preserveLastModified ) throws IOException { if ( ( overwrite || ( ! ( destFile . exists ( ) ) ) ) || ( ( destFile . lastModified ( ) ) < ( sourceFile . lastModified ( ) ) ) ) { <START_BUG> if ( destFile . exists ( ) ) { <END_BUG> destFile . delete ( ) ; } log ( ( ( ( "Copy:<seq2seq4repair_space>" + ( sourceFile . getAbsolutePath ( ) ) ) + "<seq2seq4repair_space>-><seq2seq4repair_space>" ) + ( destFile . getAbsolutePath ( ) ) ) , Project . MSG_VERBOSE ) ; File parent = new File ( destFile . getParent ( ) ) ; if ( ! ( parent . exists ( ) ) ) { parent . mkdirs ( ) ; } if ( filtering ) { BufferedReader in = new BufferedReader ( new FileReader ( sourceFile ) ) ; BufferedWriter out = new BufferedWriter ( new FileWriter ( destFile ) ) ; int length ; String newline = null ; String line = in . readLine ( ) ; while ( line != null ) { if ( ( line . length ( ) ) == 0 ) { out . newLine ( ) ; } else { newline = replace ( line , filters ) ; out . write ( newline ) ; out . newLine ( ) ; } line = in . readLine ( ) ; } out . close ( ) ; in . close ( ) ; } else { FileInputStream in = new FileInputStream ( sourceFile ) ; FileOutputStream out = new FileOutputStream ( destFile ) ; byte [ ] buffer = new byte [ 8 * 1024 ] ; int count = 0 ; do { out . write ( buffer , 0 , count ) ; count = in . read ( buffer , 0 , buffer . length ) ; } while ( count != ( - 1 ) ) ; in . close ( ) ; out . close ( ) ;

Fix:
if ( ( destFile . exists ( ) ) && ( destFile . isFile ( ) ) ) {